2014 Mercedes-Benz CLA45 AMG

AMG's first four-cylinder is insane! The car, not so much.

In rural northern Germany, a €35-million investment has transformed a munitions depot into the Bilster Berg racetrack, a 19-turn, 2.5-mile playground. Four hours south in Affalterbach, Germany’s font of tire-slaying torque is facing a similar transition. At AMG’s headquarters, rear-drive brutes like the E63 AMG are being retrofitted with all-wheel drive, and the newest creation, the 2014 Mercedes-Benz CLA45 AMG, suggests a more playful, less volatile future for Merc’s performance arm.

Putting the 911 Turbo in Its Place

At first glance, the CLA45 AMG’s basic attributes—huge power, a turbocharged four-cylinder, and all-wheel drive—draw parallels to the Mitsubishi Lancer Evolution and Subaru WRX STI. In reality, these cars exist in a different kind of parallelism: The demographics of their buyers will never intersect. For one, the rally crowd wouldn’t know what to make of an interior this nice. More divisive, though, the Subaru and the Mitsubishi don’t posses the civility and docility of the Mercedes.

Don’t confuse those traits with banality. At 178 horsepower per liter, the CLA45 just knocked off the Porsche 911 Turbo in claiming the title of most power-dense production engine in the world. AMG’s secret sauce is a BorgWarner twin-scroll turbocharger custom-made for this application and capable of producing up to 26.1 psi of boost. Thus strapped, the CLA45’s four-cylinder makes 355 horsepower at 6000 rpm and 332 lb-ft of torque at 2250 rpm. Although dimensionally identical to the CLA250’s turbo four, AMG’s M133 engine uses a stronger sand-cast—rather than die-cast—aluminum block. There’s also a low-temperature cooling circuit that feeds a water-to-air intercooler.

A butterfly valve subtly alters the exhaust note in different driving modes and conditions by metering the amount of air that flows out the passenger side of the dual exhaust system. It helps produce a soundtrack that’s deeper and louder than that of the typical four-cylinder, but the timbre isn’t particularly notable. The CLA45 does, however, emit a fulfilling bbbrrraaappp with every full-throttle upshift at redline.

Unfortunately, those upshifts aren’t as quick or direct as we expect them to be. Mercedes’ new seven-speed dual-clutch automatic was the source of our largest gripe with the CLA250, and it remains so for the CLA45. The hardware is strengthened, but the engine interface still relies on a pair of dry-clutch packs. The Volkswagen Group’s wet dual-clutch transmissions shift faster and more crisply. The launch-control program, known as Race Start, is the CLA45’s one pleasantly unpolished edge. Peck the right buttons, pull the shift paddles, and push the pedals in the correct order, and the engine spins to almost 4000 rpm before the clutch hooks up. The all-wheel-drive system sends up to 50 percent of torque to the rear wheels via a final-drive ratio that’s been reduced from 4.13:1 in the CLA250 to a really tall 2.44:1. We predict the precisely managed traction control will send the CLA45 to 60 mph in 4.4 seconds.

OMG! What Did You Do with My AMG?

AMG reworked the suspension with stiffer springs, dampers, bushings, and front knuckles. There are larger anti-roll bars, a solid-mounted rear subframe, and bigger vented and perforated brake discs. On the Bilster Berg racetrack, the CLA45 displayed excellent body control, following its Dunlop Sport Maxx RT tires obediently. The steering is as good as anything BMW turns out these days, and the suspension is compliant enough to be comfortable on the street, despite its limited travel.

Yet as competent as it is, the Mercedes-Benz CLA45 AMG feels sterile when hustled on track or road. It lacks the punch of an Evo and the sensitivity of a BMW 1-series. More disturbing, the CLA45 doesn’t have the reckless streak of other AMG models. Mercedes has made 355 horsepower and 332 pound-feet of torque in a car roughly the size of a VW Jetta feel downright civilized. The CLA45 doesn’t need to be any quicker, but we wish it would ignite its sensible, luxury-minded inhibitions in a cloud of tire smoke more often.